Automatic knife



FIG. 1 is a perspective view of an automatic knife showing our new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a back view thereof.

The broken lines in the Figures show portions of the automatic knife which form no part of the claimed design. 

CLAIM The ornamental design for an automatic knife, as shown and described. 